callback-hell

js

function buyBread (input, callback) {
  gotoStore(input, (storeErr, storeResponse) => {
    if (storeErr) {
      return callback(Error('Store is unavailable'), null)
    }
    buyBrownBread(input, (brownBreadErr, brownBreadResponse) => {
      // if unable to buy brown bread, buy white bread
      if (brownBreadErr) {
        buyWhiteBread(input, (whiteBreadErr, whiteBreadResponse) => {
          if (whiteBreadErr) {
            return callback(Error('Breads not in stock!'), null)
          }
          // success
          callback(null, whiteBreadResponse)
        })
      } else {
        // success
        callback(null, brownBreadResponse)
      }
    })
  })
}